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D( x )
x = 0
x = 0
x = 0
x in (-oo:0) U (0:+oo)
3*x-(2/5) = 8/x // - 8/x
3*x-(8/x)-(2/5) = 0
3*x-8*x^-1-2/5 = 0
3*x^1-8*x^-1-2/5*x^0 = 0
(3*x^2-2/5*x^1-8*x^0)/(x^1) = 0 // * x^2
x^1*(3*x^2-2/5*x^1-8*x^0) = 0
x^1
3*x^2+(-2/5)*x-8 = 0
3*x^2+(-2/5)*x-8 = 0
DELTA = (-2/5)^2-(-8*3*4)
DELTA = 2404/25
DELTA > 0
x = ((2404/25)^(1/2)-(-2/5))/(2*3) or x = (-(-2/5)-(2404/25)^(1/2))/(2*3)
x = ((2404/25)^(1/2)+2/5)/6 or x = (2/5-(2404/25)^(1/2))/6
x in { (2/5-(2404/25)^(1/2))/6, ((2404/25)^(1/2)+2/5)/6}
x in { (2/5-(2404/25)^(1/2))/6, ((2404/25)^(1/2)+2/5)/6 }
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